OBJECTIVES: 1. To determine whether the active transport of sodium out of the lens occurs by a saturable carrier-mediated process and the extent to which transport is coupled to the active influx of potassium. 2. To investigate possible feed-back relationships between active and passive transport of ions and bioelectric potential, as they may operate to control lens clarity through maintenance of normal lens hydration. 3. To correlate the oxidative metabolic state of the pigment epithelium with its capacity to actively extrude potassium across this structure in vitreous to blood direction as a possible factor in the control of intraocular pressure.